This invention relates to the recovery of precious metal from sulphide minerals.
As used herein the phrase “precious metal” includes gold and silver.
Commercial bioleach plants which are currently in operation treating precious metal bearing sulphide minerals, typically operate within the temperature range of 40° C. to 50° C. and rely on sparging air to the bioleach reactors to provide the required oxygen. Operation at this relatively low temperature and the use of air to supply oxygen, limit the rate of sulphide mineral oxidation that can be achieved.
The use of high temperatures between 50° C. and 100° C. greatly increases the rate of precious metal bearing sulphide mineral leaching.
The solubility of oxygen is however limited at high temperatures and the leaching rate becomes limited. In the case of using air for the supply of oxygen, the effect of limited oxygen solubility is such that the leaching rate becomes dependent on and is limited by the rate of oxygen transfer from the gas to the liquid phase.